The Correct Answer is C: Renal Artery Stenosis is Associated with Atherosclerotic Disease
Atherosclerotic disease accounts for approximately 90% of renal artery stenosis cases, making it by far the most common etiology 1. This is the definitive answer based on the highest quality guideline evidence.
Why Each Answer is Right or Wrong:
A) Fibromuscular Dysplasia is the Most Common Cause - INCORRECT
- Fibromuscular dysplasia accounts for only 10% of RAS cases 1
- While FMD is the second most common cause 2, atherosclerosis dominates at 90%
- FMD is more common in younger patients (particularly middle-aged women) but represents a minority of overall cases
B) More Common in Individuals Under Age 45 - INCORRECT
- RAS is actually more common in older individuals, particularly those over 50-55 years 3
- The ACR guidelines note that new onset hypertension after age 50 is a clinical feature suggesting renovascular hypertension 1
- Atherosclerotic RAS typically affects individuals over 55 years 3
- While FMD does affect younger patients, it represents only 10% of cases
C) Associated with Atherosclerotic Disease - CORRECT
- Atherosclerosis causes 90% of RAS 1
- Strong association exists between RAS and atherosclerosis in other vascular beds 4
- In patients with coronary artery disease, 30% have some evidence of RAS, and 15% have lesions ≥50% stenosis 4
- ARAS independently doubles mortality risk even when coronary revascularization is performed 4
D) Usually Idiopathic - INCORRECT
- RAS has identifiable causes in the vast majority of cases
- 90% atherosclerotic, 10% fibromuscular dysplasia 1
- Less common causes include vasculitis, embolic disease, dissection, and trauma 1
- "Idiopathic" is not a recognized major category
E) Renal Artery Ultrasound is Not Sensitive for Diagnosis - INCORRECT
- Duplex ultrasonography is commonly recommended as the best initial test for RAS detection 5
- Ultrasound can be utilized regardless of renal function level 1
- While sensitivity may be limited in certain situations (branch vessel disease, obesity), it remains a valuable screening tool
Clinical Context and Implications:
The atherosclerotic etiology has critical prognostic implications:
- Patients with ARAS have significantly increased cardiovascular morbidity and mortality 4
- The presence of ARAS independently predicts adverse outcomes
- These patients require aggressive atherosclerotic risk factor modification
- The severity of stenosis correlates directly with mortality risk 4
Common clinical pitfall: Assuming all RAS in younger patients is FMD—while FMD predominates in young women, atherosclerotic disease can still occur, particularly in those with risk factors 6. Conversely, patients with known FMD can develop superimposed atherosclerotic lesions as they age 6.